A search of the PubMed, EMBASE, and PsycINFO databases was conducted through March 2009 using the search terms life stress, life event, depression, depress, serotonin transporter, 5-HTTLPR, interaction, and moderation. Bibliographies of studies were also reviewed. A total of 26 articles published or set for publication were identified through this search strategy (Figure 1). Inclusion criteria for studies for the meta-analyses were published articles that included data on the association between the (1) 5-HTTLPR genotype (S, SL, or LL), (2) number of stressful life events (0, 1, 2, or ≥3) or equivalent, and (3) categorical measure of depression defined by the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) or International Statistical Classification of Diseases, 10th Revision (ICD-10) or ability to use a cut point to define depression from standardized rating scales. To maximize our ability to use a common framework for variable definition, we also requested original data from all studies that appeared to meet inclusion criteria published prior to 2008.10,15-28 We received original data in a usable format for the meta-analysis from 10 of the 14 study
